The present invention relates generally to explosive testing, and more particularly, relates to a method and a device for measuring quantitatively detonation transfer between two explosive components.
Prior attempts to evaluate explosive train performance have employed one of three general approaches:
(1) Firing randomly selected interface assemblies and inferring therefrom the probability of success by attribute (go-nogo) statistical analysis;
(2) By imposing a penalty on the detonation transfer process and using the success ratio as an indicator of transfer capability; or
(3) By real-time measurement of transfer phenomena such as transit time of the detonation front or shock pressures.
The attribute statistical analysis requires large numbers of tests to verify the high reliabilities required of detonation transfer systems. As an example, 2,300 successful transfers without any failures is required to verify a 0.999 probability of firing with 90% confidence. The go-nogo evaluation technique is insensitive to performance variations and cannot be used to evaluate the relative performance of competing designs in a transfer system.
Applications of the penalty technique have used air gaps, barriers, and explosive quantity, density, and composition as variable detonation transfer penalties. The resulting performance is evaluated by a statistical analysis such as Bruceton or Probit.
The air gap is the most commonly used penalty in testing. Variations in the air gap change several transfer parameters non-linearly. This non-linearity has not been calibrated to date and prevents extrapolation of probability estimates to the expected gap configuration. The marginal air gap used in the penalty test is normally significantly larger than the design gap and can provide misleading comparison when evaluating different designs.
Variable thickness barriers, also used in the penalty technique, vary several transfer parameters non-linearly and also modify the air gap geometry. Variable aperture barriers modify only the area of particle impact on an acceptor explosive component. The explosive sensitivity to this variable is not well established and this variable is not easily related to expected configurations.
The modifications of explosive densities, quantity, or composition require special component fabrication and must also use additional comparison techniques to relate the modified components to the actual components for probability predictions.
Thirdly, real-time measurements have been limited to very precisely aligned laboratory experiments and have not yet proven suitable for routine testing at the manufacturer's facilities. In addition, the interpretation of real time measurements has not been universally accepted in evaluating competing designs.
The present invention is directed toward providing a technique in which these undesirable characteristics are minimized.